package com.data.basic.chapter10;

import java.util.TreeMap;

/**
 *
 * 字典树，只能处理字符串
 *          基于TreeMap的实现
 *          Trie的字符位于路径之上
 * @author wang on 2018/7/3.
 */
public class Trie {


    //节点类
    private class Node{
        public boolean isWord;
        public TreeMap<Character,Node> next;
        public Node(boolean isWord){

            this.isWord=isWord;
            next = new TreeMap<>();
        }

        public Node() {
            this(false);
        }
    }

    private Node root;
    private int size;

    public Trie(){
        root = new Node();
        size=0;
    }

    //获取Trie中存储的单词数量
    public int getSize(){
        return size;
    }

    //向Trie中加入单词
    public void add(String word){

        Node cur = root;
        for (int i=0;i<word.length();i++){
            char c = word.charAt(i);

            if (cur.next.get(c)==null){
                //如果不存在就生成新节点
                cur.next.put(c,new Node());
            }
            cur = cur.next.get(c);
        }
        if (!cur.isWord){
            cur.isWord = true;
            size++;
        }
    }
    //查询Trie的单词
    public boolean contains(String word){
        Node cur = root ;
        for (int i=0;i<word.length();i++){
            char c = word.charAt(i);
            if (cur.next.get(c)==null){
                return false;
            }
            cur = cur.next.get(c);
        }
        return cur.isWord;
    }


    //前缀搜索   查询是否有单词以prefix为前缀
    public boolean isPrefix(String prefix){
        Node cur = root;
        for (int i=0;i<prefix.length();i++){
            char c = prefix.charAt(i);
            if (cur.next.get(c)==null){
                return false;
            }
            cur = cur.next.get(c);
        }
        //遇上面的不同，不需要判断isWord
        return true;
    }
}
